This invention relates to a magnetic head displacing means for a magnetic disc recording and reproducing device.
Conventionally, a magnetic disc recording and reproducing device generally includes a rotatable magnetic disc, a magnetic head for reading/writing information on the magnetic disc, a magnetic head displacing mechanism for displacing the magnetic head in the direction of a radius of the magnetic disc, and an electric motor for actuating the magnetic head displacing mechanism. The magnetic head displacing mechanism is actuated by the motor to displace the magnetic head across a plurality of tracks, which are arranged on the magnetic disc in concentric circles and are spaced each other in the order of micron meters, and to locate the magnetic head accurately on a desired track. Two types of magnetic head displacing mechanisms have been utilized, one of which is called a linear type wherein rotational movement of the output shaft of the motor is converted into a linear movement of the magnetic head, and the other of which is called a swing arm type wherein the rotational movement of the output shaft of the motor is converted into a pivotal movement of a swing arm on which the magnetic head is mounted to move along an arcuate path extending generally in the direction of a radius of the magnetic disc.
In either type of the magnetic head displacing mechanisms, it is required that the magnetic head displacing mechanism not displace casually in its inactuated condition because of an external force due to such conditions as transportation, vibrations, and the like. To this end, a brake or lock mechanism has been provided for preventing casual rotation of the motor in the inactuated condition of the motor. Further, it is required that the magnetic head displacing mechanism accurately stop on a desired track despite the inertia force acting on moving parts. To satisfy such requirements there has been proposed a damping mechanism on the magnetic disc device.
Further, in locating the magnetic head on a desired track it is required to displace the magnetic head accurately with respect to a reference position or a reference track.